Satellites or other space vehicles are configured to orbit around a planet, such as the Earth, for a variety of purposes, such as communications, exploration, etc. For example, a geosynchronous satellite is a satellite that orbits the Earth and follows the direction of the Earth's rotation. One revolution of a geosynchronous satellite around the Earth takes about 24 hours, which is the same amount of time it takes for the Earth to rotate once about its axis. These types of satellites are considered geosynchronous because they appear stationary when viewed from a particular location on the Earth, and are commonly used as communication satellites.
When a satellite is in orbit, systems onboard the satellite are able to control the orientation of the satellite in relation to a planet, which is referred to as attitude control. For example, attitude control systems are able to control the orientation of a satellite so that instruments (e.g., antennas, telescopes, cameras, etc.) onboard the satellite point in a desired direction.
Traditional satellites use chemical thrusters (e.g., bipropellant) and/or reaction wheels for attitude control. A reaction wheel uses a spinning mass with a substantial amount of inertia. The spinning mass of the reaction wheel applies torque along an axis of the satellite causing a rotation of the satellite along that axis. Installation of a reaction wheel along three axes of the satellite, for example, allows systems to control the rotation of the satellite along all three axes. The chemical thrusters may be used to assist the reaction wheels in attitude control.
It is desirable to identify new and improved ways for controlling the attitude of space vehicles.